The lithosphere is the solid outer layer of the Earth. It consists of the Earth's crust and its upper mantle.
The word lithosphere comes from the Greek word lithos which means "stone." As the Earth's crust and its upper mantle have a similar composition, scientists have grouped them together under the term lithosphere (shown at #4 in the image below).
The lithosphere varies in thickness, reaching over 150 km. It rests on a fluid mantle, one of the superimposed layers making up the Earth’s internal structure. Also, rather than forming a perfect sphere, it is divided into several tectonic plates. Most of the known geological phenomena take place in the lithosphere.
It is sometimes assumed that the lithosphere constitutes only the continents. However, the lithosphere is also found beneath the oceans. The latter would be more easily observed if all the water were removed from the Earth's surface. We can therefore distinguish a thin oceanic lithosphere (under the oceans) and a thicker continental lithosphere.
On the surface, the earth is shaped in several different reliefs such as mountains, plains, and plateaus. Solid elements are found in the soil, like rocks, but also liquid portions, for example, water tables and petroleum.
The lithosphere is essential for sustaining life; it provides a rooting base for plants and the elements necessary for their growth, such as carbon, nitrogen, and phosphorus. Plants are the basis of food chains. Human beings also depend on the lithosphere since it supplies many mineral and petroleum resources.
Human beings are in a constant relationship with the lithosphere. The latter allows plants to grow and draw the water and minerals they need to survive. Humans cultivate these plants for food or clothing.
Human beings inhabit the lithosphere. The construction of houses requires the use of materials from the soil such as sand or petroleum.
In a similar vein, humans exploit the lithosphere by building mines from which they draw the minerals necessary to create the various products that satisfy their needs.
Human beings also act by transforming the lithosphere, in particular by releasing residual matter that modifies the lithosphere’s constitution.
Finally, humans transform some natural resources in the lithosphere into energy (fossil fuels, geothermal energy, nuclear energy) in order to meet their daily needs.